The technique of packaging one or more articles using a heat-shrink sleeve made in the form of a sleeve that is engaged over the article(s) to be packaged and that is then heat-shrunk onto said article(s) has already been in use for about thirty years. The technique of heat-shrinking by applying a heat field to the outside of the sleeve in order to shrink the sleeve uniformly onto the article, even when said article is of section that varies greatly, is now thoroughly mastered. As an indication, it is now possible to achieve shrinkage ratios of as much as 70% to 80% in section. Anamorphosis techniques enabling printing to be performed on the sleeve so that the printing remains readable after the sleeve has been shrunk onto an article are also thoroughly mastered, with this being particularly important in the fields of pharmaceuticals and cosmetics.
Until now, printing techniques have been restricted to conventional techniques consisting in applying decoration that presents controlled anamorphosis during shrinkage of the sleeve on the article(s) to be packaged.
The technological background of the invention is illustrated by documents EP-A-0 537 445 and U.S. Pat. No. 6,020,823, which are described briefly below.
Document EP-A-0 537 455 describes registration marking applied to an elastic packaging sheet so as to obtain a pattern (in particular a screen pattern) which remains when the sheet is stretched. Nevertheless, that document relates to thermoplastic sheets which are stapled to pallets, and it does not relate to heat-shrink sleeves.
Document U.S. Pat. No. 6,020,823 describes fastening sound or light-emitting articles to a bottle, by using a heat-shrink sleeve. The sleeve may be of single thickness, in which case the articles are stuck to the inside face of the sleeve, prior to the sleeve being put into place on the bottle and shrunk, or it may have two thicknesses, in which case the articles are sandwiched between two sheets (which may be heat-shrink or otherwise). It should be observed that the relief that is apparent on the outside is no more than the outline of the article that is held captive, as can be seen clearly from FIG. 6.